Log Message:
libextractor: Fix various dependencies.

- Add msgfmt msgmerge xgettext to USE_TOOLS, it needs these
- Fix building with libjpeg-turbo by using the correct buildlink
- Use newer multimedia/mp4v2 over multimedia/libmp4v2 to avoid conflicts
  This is confusing. I think we mainly keep libmp4v2 around for KDE4.
  But the packages could be named better.